The invention relates to a system and a method for emitting an audio signal in an environment. More specifically the invention relates to a system for emitting an audio signal in an environment, the system comprising: an audio source for providing the audio signal, at least one loudspeaker for emitting the audio signal, and at least one microphone for receiving an acoustic signal from the environment, whereby the acoustic signal is based on the audio signal and may comprise disturbing components. The invention also relates to a method using the system.
Public address systems or other systems for emitting audio signals, like music, speech or announcements, in different locations like supermarkets, schools, universities, auditoriums are widely known. These systems usually comprise an audio source, for example a microphone or a recorder, and a plurality of loudspeakers, which are locally distributed in the locations, for emitting the audio signal from the audio source.
In simple embodiments, these systems have an adjustable amplification, so that the volume of the audio signal emitted by the loudspeakers can be adjusted to a desired value. In more sophisticated systems, the amplification is made dependent from the noise and other disturbing components in the locations. In some of these systems a signal to noise ratio (SNR) is calculated, which is often determined as the quotient: (amplified output)/(sensed ambient signal-amplified output), whereby the sensed ambient signal may be detected by a microphone in the locations. Such an approach is for example disclosed in the document U.S. Pat. No. 5,434,922 A in the connection of a radio for an automobile.
Document EP 1 808 853 A 1, probably representing the closest prior art, discloses a public address system which compares a wanted audio signal with a disturbing audio signal and calculates an amplification factor for amplifying the audio signal.